Annotate System.Diagnostics.EventLog with Nullable Reference Types

src/libraries/Common/src/Interop/Windows/Advapi32/Interop.ClearEventLog.cs

@@ -10,6 +10,6 @@ internal static partial class Advapi32
     {
         [LibraryImport(Libraries.Advapi32, EntryPoint = "ClearEventLogW", SetLastError = true, StringMarshalling = StringMarshalling.Utf16)]
         [return: MarshalAs(UnmanagedType.Bool)]
-        public static partial bool ClearEventLog(SafeEventLogReadHandle hEventLog, string lpBackupFileName);
+        public static partial bool ClearEventLog(SafeEventLogReadHandle hEventLog, string? lpBackupFileName);
     }
 }

src/libraries/Common/src/Interop/Windows/Advapi32/Interop.ReportEvent.cs

@@ -16,7 +16,7 @@ public static partial bool ReportEvent(
             short wType,
             ushort wcategory,
             uint dwEventID,
-            byte[] lpUserSid,
+            byte[]? lpUserSid,
             short wNumStrings,
             int dwDataSize,
             IntPtr lpStrings,

src/libraries/Common/src/System/Diagnostics/NetFrameworkUtils.cs

@@ -14,13 +14,13 @@ namespace System.Diagnostics
 {
     internal static partial class NetFrameworkUtils
     {
-        internal static void EnterMutex(string name, ref Mutex mutex)
+        internal static void EnterMutex(string name, ref Mutex? mutex)
         {
             string mutexName = "Global\\" + name;
             EnterMutexWithoutGlobal(mutexName, ref mutex);
         }
 
-        internal static void EnterMutexWithoutGlobal(string mutexName, ref Mutex mutex)
+        internal static void EnterMutexWithoutGlobal(string mutexName, ref Mutex? mutex)
         {
             Mutex tmpMutex = new Mutex(false, mutexName, out _);
 
@@ -44,7 +44,7 @@ internal static void EnterMutexWithoutGlobal(string mutexName, ref Mutex mutex)
         // just to allow us to poll for abort). A limitation of CERs in Whidbey (and part of the problem that put us in this
         // position in the first place) is that a CER root in a method will cause the entire method to delay thread aborts. So we
         // need to carefully partition the real CER part of out logic in a sub-method (and ensure the jit doesn't inline on us).
-        private static bool SafeWaitForMutex(Mutex mutexIn, ref Mutex mutexOut)
+        private static bool SafeWaitForMutex(Mutex mutexIn, ref Mutex? mutexOut)
         {
             Debug.Assert(mutexOut == null, "You must pass in a null ref Mutex");
 
@@ -68,7 +68,7 @@ private static bool SafeWaitForMutex(Mutex mutexIn, ref Mutex mutexOut)
         // The portion of SafeWaitForMutex that runs under a CER and thus must not block for a arbitrary period of time.
         // This method must not be inlined (to stop the CER accidently spilling into the calling method).
         [MethodImplAttribute(MethodImplOptions.NoInlining)]
-        private static bool SafeWaitForMutexOnce(Mutex mutexIn, ref Mutex mutexOut)
+        private static bool SafeWaitForMutexOnce(Mutex mutexIn, ref Mutex? mutexOut)
         {
             bool ret;
 
@@ -117,8 +117,8 @@ private static bool SafeWaitForMutexOnce(Mutex mutexIn, ref Mutex mutexOut)
         internal static string GetLatestBuildDllDirectory(string machineName)
         {
             string dllDir = "";
-            RegistryKey baseKey = null;
-            RegistryKey complusReg = null;
+            RegistryKey? baseKey = null;
+            RegistryKey? complusReg = null;
 
             try
             {
@@ -133,25 +133,25 @@ internal static string GetLatestBuildDllDirectory(string machineName)
                 complusReg = baseKey.OpenSubKey("SOFTWARE\\Microsoft\\.NETFramework");
                 if (complusReg != null)
                 {
-                    string installRoot = (string)complusReg.GetValue("InstallRoot");
+                    string? installRoot = (string?)complusReg.GetValue("InstallRoot");
                     if (installRoot != null && installRoot != string.Empty)
                     {
                         // the "policy" subkey contains a v{major}.{minor} subkey for each version installed.  There are also
                         // some extra subkeys like "standards" and "upgrades" we want to ignore.
 
                         // first we figure out what version we are...
                         string versionPrefix = "v" + Environment.Version.Major + "." + Environment.Version.Minor;
-                        RegistryKey policyKey = complusReg.OpenSubKey("policy");
+                        RegistryKey? policyKey = complusReg.OpenSubKey("policy");
 
                         // This is the full version string of the install on the remote machine we want to use (for example "v2.0.50727")
-                        string version = null;
+                        string? version = null;
 
                         if (policyKey != null)
                         {
                             try
                             {
                                 // First check to see if there is a version of the runtime with the same minor and major number:
-                                RegistryKey bestKey = policyKey.OpenSubKey(versionPrefix);
+                                RegistryKey? bestKey = policyKey.OpenSubKey(versionPrefix);
 
                                 if (bestKey != null)
                                 {
@@ -191,7 +191,7 @@ internal static string GetLatestBuildDllDirectory(string machineName)
                                                 continue;
                                             }
 
-                                            RegistryKey k = policyKey.OpenSubKey(majorVersion);
+                                            RegistryKey? k = policyKey.OpenSubKey(majorVersion);
                                             if (k == null)
                                             {
                                                 // We may be able to use another subkey